Advances in solid state electronics over the last half-century have been predicated predominantly on improvements to and specialization of devices based on a p-n junction (also referred to herein as PN junction). Such improvements have been aimed at every aspect of device performance, from increased efficiency and yield to optimized frequency response, minimized noise, and more. Common p-n junction-based devices include diodes, transistors, triodes, LED's (including OLED's), etc. Such p-n junction-based devices form the core of the modern electronics industry.
However, the basic p-n junction has some fundamental and unavoidable drawbacks, some of which stem from the physical p-n junction itself. For example, the p-n junction requires the extrinsic doping of intrinsically electrically neutral semiconductor material with positive or negative ions to create the respective p- or n-type materials forming the junction. Such doping is expensive, can damage the semiconductor lattice, and increases scattering centers that can decrease carrier mobility and increase resistance. Further drawbacks of traditional p-n junction devices owe to subtleties in the physical motions of carriers within the junction, p-n band structure, and more, leading to various problems in creating exceptionally high-conductivity, high current, high power, and high frequency devices. Finally, PN junctions may be limited by the solid solubility of their constituent materials.
Moreover, as mentioned above, PN junctions are formed via doping where dopants, as Coulomb scattering center, results in high scattering with low mobility; whereas field effect transistors (“FETs”) utilize boundary conditions result in charge transfer without Coulomb Centers for scattering of carriers. With the advent of Type III Heterostructures, where the valence band maximum of one may be above the conduction band minimum of the other, resulting in transfer of carriers from the filled valence band to be transferred to the adjacent empty conduction band, resulting in carrier transfer without doping. Depending on the hetero-structures involved, this type of carrier transfer may be way above the traditional solid solubility limit.
Unfortunately, the extra charges as center for scattering with drastic reduction of mobility as Coulomb scattering centers, which is the reason why PN-junctions are relegated to rectifiers as most semiconducting devices utilize metal-oxide-semiconductor field-effect transistor (“MOSFET”), and not PN junctions.